Near infrared -silica

Spectrometer was used. Normal operating conditions were used normal slit, IX expansion, 12-minute scan speed (4000-200 wave numbers), and normal gain, in accordance with Perkin-Elmer setup instructions. A Beckman 2 cm path length, near infrared silica cell (holds 8 ml sample) was used to hold the desorbing solution in the sample compartment (Figure 1). 

Changes of fibre optical properties and thus changes of the analyte can be detected in the ultraviolet (UV), visible (VIS), near infrared (NIR) and middle/far infrared (IR) regions. There are only a few materials sufficiently transparent in the UV region, and among them, the pure silica is uniquely suitable for fibre drawing. From Figure 5 it can be seen that the UV... 

Technician Velma Montoya, of the Actinide Analytical Chemistry Group at Los Alamos, works in a silica-free glove box to determine silicon content in plutonium samples using visible (near infrared) spectrophotometry. 

Bringley JF, Penner TL, Wang R, Harder JF, Harrison WJ, Buonemani L (2008) Silica nanoparticles encapsulating near-infrared emissive cyanine dyes. J Colloid Interface Sci 320 132-139... 

The optical properties of a DDSN are mainly determined by the properties of dye molecules. Since silica nanomaterials are effectively transparent they are unlikely to absorb light in the near-infrared, visible or ultraviolet regions, which allows the dye molecules inside the silica matrix to keep their original optical properties [64]. Meanwhile, the presence of the silica matrix provides a new environment for dye molecules and affects dye fluorescence properties. 

Normal glass will only transmit radiation between about 350 nm and 3 /rm and, as a result, its use is restricted to the visible and near infrared regions of the spectrum. Materials suitable for the ultraviolet region include quartz and fused silica (Figure 2.28). The choice of materials for use in the infrared region presents some problems and most are alkali metal halides or alkaline earth metal halides, which are soft and susceptible to attack by water, e.g. rock salt and potassium bromide. Samples are often dissolved in suitable organic solvents, e.g. carbon tetrachloride or carbon disulphide, but when this is not possible or convenient, a mixture of the solid sample with potassium bromide is prepared and pressed into a disc-shaped pellet which is placed in the light path. 

The synthesis of a new near-infrared cyanine dye was monitored by CE and fluorescence detection. The chemicals structure of the dye and its synthetic precursor are depicted in Fig. 3.165. The analysis of the dye was realized in fused-silica capillaries of 75 and 100 /an i.d. The total and effective lengths of capillaries were 75 and 60 cm, respectively. The separation voltage was 30 kV and separations were carried out at ambient temperature. The running buffer was 2.5 mM Na2B407 (pH = 9.2). A near-infrared laser-induced fluorescence detector was applied. Electropherograms illustrating the separation of the dye are shown in Fig. 3.166. 

Vitreous silica has a wide range of commercial and scientific applications. Its unique combination of physical properties includes good chemical resistance, minimal thermal expansion, high refractoriness, and excellent optical transmission from the ultraviolet to the near-infrared. 

Optical Properties. The optical transmission of vitreous silica is influenced by impurities and the forming process. Ultrapure vitreous silica has the ability to transmit from the deep ultraviolet, through the visible, and into the near-infrared spectral range. 

Fong A, Hieftje GM. Near Infrared measurement of relative and absolute humidity through detection of water adsorbed on a silica gel layer. Anal Chem 1995 67 1139-1146. 

THG measurements on poly- -butylCOT films, referenced to a bare fused silica plate, were made using 1064 nm pulses. These measurements showed that the l/(3)l values of films of poly-rt-butylCOT, lxl0 10 esu, were comparable to that for unoriented polyacetylene at the same wavelength (39). However, comparison of the linear transmission spectra of these materials in the near infrared shows that the partially substituted polyacetylene has greatly improved optical quality. (See Figure 7.)... 

The photograph presented in Figure 13.10 shows a typical interface used to collect these noninvasive spectra. Light is incident on one side of the skinfold and a fraction of the transmitted light is collected directly from across the input fiber. Bundles of low-hydroxy silica fibers are used to deliver and collect the near-infrared radiation for the measurement. For the experiments described here, the noninvasive spectra were collected with a Fourier transform spectrometer set for a resolution of 16 cm-1 and 128 coadded interferograms. Each recorded spectrum required approximately 60 s to acquire and save. A total of 370 spectra were collected over a period of nearly 7h while in vivo glucose concentrations varied from 6 to 33 mM (108-594 mg/dL). 

Red and Near Infrared Photoluminescence Bands in Silica Nanostructures. 83... 

In order to assign the red and near infrared PL spectra observed experimentally for heat-pretreated MSs and silica nanoparticles (shown in Figure 4.4), we considered model clusters with various combinations of two types of the point defects, NBO and OV, with OV located 2-5 layers of Si-0 bonds away from NBO [57-59]. In our calculations, we used much larger clusters as compared to those in the previous studies, the defect areas were surrounded by at least two layers of Si-O bonds (Figure 4.5), and only... 

Another important method for photonic crystal fabrication employs colloidal particle self-assembly. A colloidal system consists of two separate phases a dispersed phase and a continuous phase (dispersion medium). The dispersed phase particles are small solid nanoparticles with a typical size of 1-1000 nanometers. Colloidal crystals are three-dimensional periodic lattices assembled from monodispersed spherical colloids. The opals are a natural example of colloidal photonic crystals that diffract light in the visible and near-infrared (IR) spectral regions due to periodic modulation of the refractive index between the ordered monodispersed silica spheres and the surrounding matrix. 

On the other hand, imique physical properties and potential applications of nanoscaled lanthanide-doped LaFa have been discussed in many reports. For instance, van Veggel et al. reported the bright white light through up-conversion of a single near-infrared source by thin film of LaFaiYb, Eu /Er /Tm NPs (Figure 65) (Sivakumar et al., 2005). And the silica films with (Er +, Nd +, and Ho ) doped LaFs NPs possessed the visible white luminescence (Sudarsan et al., 2005). 

Separation of amino acids and their identification in different mixtures are frequent tasks encountered in biochemistry. Thin layer chromatography is a fast, simple, and inexpensive approach to attain this goal. Because some of the components are UV-inactive, other methods, such as vibrational spectroscopy, should be applied for detection and identification. Comparative study based on Raman spectroscopy of thin layer chromatography spots of some weak Raman scatterers (essential amino acids) was carried out using four different visible and near-infrared laser radiation wavelengths 532, 633,785, and 1064 nm. The best results were obtained with simple silica gel plates. 

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